Chapter 17 - Air Cooled Heat Exchanger (ACHE)

Air coolers, or fin fans, are utilized globally in modern process facilities. Air is quickly moved past the tube exterior by way of a large fan system. As the product travels through the tubes, this process transfers the heat from the product into the atmosphere. An air cooler or fin fan unit is constructed of several hundred to several thousand externally finned tubes. Tube dimensions typically range from 1” (25.4mm) to 1.5” (38mm) in diameter and up to 75’ (23m) in length. Internal fouling of the tubes is a common problem, which ultimately leads to internal corrosion or pitting-type damage. Because the exterior fin/tube surface is exposed to the natural elements, a leak can result in product being released into the atmosphere.

The design of air cooled heat exchangers is governed by API-661, ASME Section VIII notably appendix 13 for  header design ISO 13706. A fin fan is an air-cooled heat exchanger. Instead of dissipating heat into water and then transferring that heat to the air, as with shell and tube heat exchangers and wet cooling tower systems, a fin fan dissipates heat from a fluid directly into the air. Forced air fans located below the piping are used to cool quench water, and induction fans located above the piping are used for lower temperature applications. While fin fans can be powered by a variety of sources -- steam turbines, natural gas or gasoline engines, electric motors and hydraulic motors. Fin fan heat rejection does not require a water source. Process applications requiring large amounts of cooling need not be located near a water supply. However, a fin fan's heat rejection ability is linked directly to drive system efficiency.


Above is an excerpt from the chapters of the book: Detail Engineering and Layout of Piping Systems 5th Edition.
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